Door opening and closing mechanism



5 Sheets-Sheet l Jan. 6, 1953 R. E. PETERSON DOOR OPENING AND CLOSINGMECHANISM Filed March 24, 1950 INSIDE OUTSIDE OUTSIDE Jan. 6, 1953 R. E.PETERSON DOOR QPENING AND CLOSING MECHANISM Filed March 24, 1950 3Sheets-Sheet 2 Jan. 6, 1953 R. E. PETERSON DOOR OPENING AND CLOSINGMECHANISM Filed March 24, 1950 3 Sheets-Sheet 5 ,Zrzmezziar ZMwEM/AvwPatented Jan. 6, 1953 UNITED STATES PATENT OFFICE DOOR OPENING tiiismcMECHANISM Reuben E. Peterson, Fergus Falls, Minn.

Application March 24, 1950, Serial No. 151,716

- My invention relates generally to automatic door-opening and closingmechanism and, more specifically, to mechanism for opening a, doorresponsive to the presence of trafiic on one side thereof and forclosing the door responsive to the presence of traffic on the other sidethereof.

I am aware that automatic door-opening and closing mechanisms, whichinclude electronic apparatus and motors for opening a door, are in useat present. However, my invention contem- 7 plates the use of relativelyinexpensive fluidpressure means and novel switch mechanism operatedthereby to control operation of a door.

An important object of my invention is the provision of door-operatingmechanism including fluid pressure-operated switches and means onopposite sides of a door, whereby said switches may be operated tocontrol door-operating mech- Still another-object of my invention is theprovision of means for operating a fluid pressureoperated switch, saidmeans being in the nature of a mat adapted to lie in the path of trafficmoving toward or from said door, said mat containinga resilient tubeextending thereabout in serpentine fashion and having connectionstherewith to said switch.

Other highly important objects and advantages of my invention willbecome apparent from the following detailed specification, appendedclaims, and attached drawings. 7

Referring to the drawings, wherein like characters indicate like partthroughout the several views Fig. 1 is aview partly in plan and partlyin diagram of my novel door-operating mechanism,

some parts being broken away and some parts L shown in section;

Fig. 2 is an enlarged fragmentary view in elevation as seen from theline 2-2 of Fig. 1, some parts being broken away and some parts shown insection;

'1 Claims. (01. 268-34) 2 V Fig. 3 is an enlarged view in side elevationof a fluid pressure-operated switch made in accordance with myinvention, some parts thereof being broken away and some parts beingshown in section; T

Fig. 4 is a view partly in vertical section and partly in diagram of anelectrically-operatedcontrol valve of my invention; 5

Fig. 5 is an enlarged fragmentary section taken on the line 5--5 of Fig.1; and Fig. 6 is a view corresponding to Fig. 3, but showinga modifiedform of switch. 1 My novel door-opening and closing mechanis is adaptedfor use with swinging or sliding doors or gates for the admittance ofany type of tr'afiic, but, preferably and as shown, is applied to aswinging door for the passage of pedestrian traffic through the openingtherefor. In the drawings, a door is indicated by the numeral l and ishingedly mounted, as at 2, in a door-opening 3 of a door casing or wall4, from a normally closed position, as indicated by full lines in Fig.1', to an outwardly-open position indicated by dotted lines in Fig. 1.In its closed position, the door I nor.- mally rests against theconventional stop strips 5. For imparting opening and closing movementsto the door I, I provide a door-operating motor in the nature of a fluidpressure cylinder 6 and a cooperating piston-equipped plunger 1. Thecylinder 6 is pivotally mounted to a bracket 8 rigidly secured to agenerally rectangular frame 9, which is secured to the upper endportion, of the door casing or wall 4 by any suitable means. The outerend of the piston plunger 1 is rigidly secured to a cross head 10, whichis mountedfor sliding movements laterally of the door opening 3 on apair of spaced parallel slide rods II that are rigidly secured at oneend to a pair of brackets l2 welded or otherwise secured to the frame 9intermediate its ends and at their opposite ends to an end wall l3 ofthe frame 9. Dooropening movements are imparted to the cross head [0 byfluid under pressure being introduced to one end of the cylinder 6through a conduit, whereas door-closing movements are imparted theretoby a coil tension spring I5 anchored at its opposite ends to the crosshead H] and the end of the frame 9 opposite the end wall l3 thereof. Adepending portion I6 of the cross head 10 extends downwardly through aslot IT in the bottom wall of the frame 9 and has ball and socketengagement with one end of a rigid link |8, the other end of which hasball and socket engagement with one end of a rigid arm 19, as indicatedat 20. The arm I9 is curved in the direction of the door I about theaxis of the hinge 2, and is provided at its inner end with a mountingplate 2|, which is screwed or otherwise rigidly secured to the door I.As indicated by full and dotted lines in Figs. 1 and 2, movements of thecrosshead H) from the right to the left with respect to these figurescauses the door I to open to an extent approximating ninety degrees ofcircular movement; whereas movement of the crosshead I in the oppositedirection causes the door I to close against the stop strips 5.

Fluid under pressure for motivating the door operating mechanism which,in this instance, may be assumed to be air, is conducted through theconduit [4 from a pressure tank or other source not shown and iscontrolled by a conventional air transformer or pressure regulator valve22 and an electrically-operated directional control 23. With referenceparticularly to Fig. 4, it will be seen that the control 23 comprises avalve body 24 having inlet and outlet valve chambers 25 and 26respectively, a passage 2?, and a chamber 28. The chamber 28communicates with the passage 21 and with the valve chambers 25 and 26through short passages 29 and 35 respectively. A flexible rubber-likediaphragm 3| defines one wall of the chamber 23 and is held in place bya retainer plate 32 and mounting screws or the like 33. The plate 32 isprovided with a pair of apertures 34 and 35 that are axially alignedwith the passages 29 and 30 respectively. A valve element 38 is seatedin the valve chamber 25 and is provided with a stem 31 which projectsdownwardly through the passage 29 in the direction of the diaphragm 3|.Valve element 36 is yieldingly biased toward a valve-closed position bya coil compression spring 38. Valve element 39, similar to the valveelement 38, is biased toward a valve-closed position in the valvechamber 26 by a coil compression spring 45 and is provided with a stem4| extending downwardly through the passage 30 and the chamber 28. Thevalve chamber 26 is open to atmosphere through a metering valve 42,whereas the valve chamber 25 communicates with the pressure regulatorvalve 22 through a portion of the conduit M. The passage 21 terminatesin a port 43 which is threaded to receive the portion of the conduit l4leading to the fluid pressure cylinder 6.

A casing 44 for the control 23 houses relayoperated mechanism formanipulating the valve elements 36 and 39, which mechanism comprises arelay coil 45, an armature 4S therefor pivoted intermediate its ends asindicated at 47, and a T-shaped lever 43. The lever 48 is pivoted in thecasing 44 as at 49, the cross bar portion 50 thereof being provided atits opposite ends with thrust pins or the like and 52, which extendupwardly into the openings 34 and 35 respectively, whereby to engage thediaphragm 3| for valve-operating movements against the valve stems 37and 4|. The armature 45 is adapted to move the lever 48 when the relaywinding 45 is energized against bias of a tension spring 53 secured atits opposite ends to the lever 48 and an anchoring pin or the like 54 inthe casing 44. As shown in Fig. 4, energization of the relay winding 45causes the armature 46 to move the lever 48 against bias of the spring53 to a position where the thrust pin 5| moves the diaphragm 3| and theoverlying valve element 36 upwardly against bias of the spring 48sufiiciently to permit air to enter the chamber 28 and flow from thencethrough the passage 21 and conduit M to the cylinder 6. When the relaywinding 45 is de-energized, the

lever 48 will be moved by the spring 53 in a direction to permit closingof the valve 35 and to move the valve element 39 to a valve-openposition, which will permit flow of air from the cylinder 6 through theconduit I4 and the passage 21 to atmosphere through the passage 30, thevalve chamber 26, and the metering valve 42 under return movements ofthe piston plunger 1 and crosshead I!) under bias of the spring l5.

The electro-magnetic winding 45 is energized to cause air under pressureto flow to the cylinder 6, and tie-energized to permit air to escapefrom the cylinder 6 to atmosphere, by a pair of switches 55 and 55, anelectro-magnetic switch actuator 51, and electrical circuits therefor.The switches 55 and 56 are in a normally open position and are mountedin a casing 58 which, together with the switch actuator 57, the control23, and parts of the door-operating mechanism, are contained within theframe 9 (see particularly Fig. 2). It may be assumed that a cover platenot shown extends over the area of the frame 9 to conceal the partscontained therein. The switch actuator 51 comprises a pair ofelectro-magnetic or solenoid windings 59 and 65 for respective armatures6| and 62 and a pair of mercury switches 63 and 64 mounted for commonmovements in a bracket 55 pivotally mounted, as indicated at 66, betweenthe depending portions of the armatures 6| and 62. As shown in Fig. 1,the outer end portion of the mercury switch 63 extends between a pair offingers B7 projecting outwardly from the lower end portion of thearmature 6|, and the outer end portion of the mercury switch 64similarly extends between a pair of fingers 68 projecting outwardly fromthe lower end portion of the armature 62. Energization of the winding 59causes upward movement of the armature 6| and rocking movement of thebracket 65 and the mercury switches 53 and 54 secured thereto to theposition indicated in Fig. 1, the armature 62 being moved downwardlywith respect to the winding by reason of its engagement with the mercuryswitch 54. Conversely, energization of the winding 60 causes upwardmovement of the armature 62 and rocking movement of the bracket andswitches 63 and 64 in the opposite direction with consequent downwardmovement of the armature 8| with respect to the winding 59.

The switch 63 is provided with a pair of contact elements 69 and 10, andthe switch 64 is likewise provided with a pair of contact elements 1|and 12. The contacts 69 and H are adapted to be connected to a source ofpotential not shown by a common lead 13 in which is interposed a switch14. The contacts 69 and 10 are interposed in a normally open controlcircuit comprising the lead 13 and switch 14, a lead 15 extending fromthe contact 10 to one side of the switch 56, a lead 16 extending fromthe opposite side of the switch 56 to the solenoid winding 60, and alead 11 extending from the opposite end of the winding 60 to the sourceof potential not shown. The contacts ll and 12 of the switch 14 areinterposed in a second normally open control circuit comprising thecommon lead I3 and switch 14, a lead 18 extending from the contacts 72to one side of the switch a lead 19 connecting the other side of theswitch 55 with one end of the solenoid winding 59, and a lead connectingthe opposite end of the winding 59 with the lead 11. The electromagneticwinding 45 of the control 23 is interposed in a circuit comprising thelead 15, a lead 8| extending from the lead 15 to one end of the .winding45, and a lead 82 connecting the other end ofthe winding 45 and the lead86, and a portion of the lead 11. t

From the above, it will be seen that closing of the switch 55 will causeenergization of the solenoid winding 59, thereby moving the mercuryswitches 63 and 64 to a switch-closed position of the switch 63. Closingof this switch completes the circuit through the relay winding 45 toenergize the same, whereby to open the valve 36 and permit air underpressure to be fed to the cylinder 6. The switches 55 and 56, being ofthe momentary contact type, remain closed only as long; as closingpressure is exerted thereon. Assuming that the switch 55 is open,closing of the switch 56 causes the solenoid winding 60 to be energized,whereby to close-the switch 64 and open the switch 63. Opening of theswitch 63 causesthe relaywinding 45-of the control 23 to be de-energizedwhereupon the spring 53 will be permitted to close the valve 36 and openthe valve 39, thus allowing air to escape from the cylinder 6 throughthe metering valve 42 to atmosphere.

I provide novel means for selectively closing the separate switches 55and 56 when it is desired to open or close the door I. Mounted withinthe casing 58 are a pair of generally U-shaped tubular elements 83 and84, the former having one end underlying the switch 55 and the latterhaving one end underlying the switch 56. The tubular elements 83 and 84,and parts contained therein, are identical, and, for the sake ofbrevity, but one of them is shown and described in detail.

Referring to Fig. 3, it will be seen that the tubular element 83 hascontained, in the lower portion thereof, a body of mercury X whichextends upwardly into the opposite legs thereof and is normally inequilibrium therein. In the leg of the tubular element 83 underlying theswitch 55, is a float 85 which may be of any suitable material having aspecific gravity less than that of the mercury X. A plunger rod 86 issecured to the float 85 and projects upwardly through the open end ofthe tubular element 83 in the direction of the switch 55. The other endof the tubular element 83 is connected with a fluid pressure conduit 81,which extends downwardly to the floor adjacent the inside of the door Iand communicates with one end of a resilientlywalled chamber 88 which,preferably and as shown, is defined by a length of rubber-like tubing 89secured to the bottom surface of a rubber mat or the like 96. Byreference to Fig. 1, it will be seen that the tube 89 extends over thegreater part of the mat area in serpentine fashion, the free end of thetube 89 being closed. Weight of a person stepping on to the mat 96 issufiicient to compress a portion of the resilient tube 89, whereby todisplace a portion of the fluid in the chamber-88, the fluid in thisinstance being air. This displacement is transmitted through theconduit-8l to the tubular element 83, causing the mercury X to raise thefloat 85 and plunger rod 86 sufficiently to close the switch 55. Amoisture trap for the conduit 81 comprises an opening 91, which ispacked with cotton or the like 92. The cotton packing 92 is suflicientlydense to prevent undue escape of air therethrough, and any moisturecontained within the conduit 81 will be absorbed thereby.

A conduit 93 extends from'the tubular element 84 downwardly to the flooror ground outside of the door I and terminates in a pressure chamberdefined. by a resilient tube orthe-like- 94 on the bottom side of a mat95. The tube 94 and .mat are identical to the tube 89 and mat 96 on theinside of the door, and it is felt that further detailed descriptionthereof is unnecessary.

It should be understood that the arrangement herein shown and describedprovides "for traffic passing through the door opening 3 in a singledirection, that is, from the inside to the outside of the door. When itis desired for a person to pass through the door opening 3, the personmerely steps upon the mat 96, whereby the displacement of air in thetube 89 causes the switch 55 to be closed by the plunger 86 of thetubular element 83. Closing of the switch 55 energizes theelectro-magnetic winding .59 and causes closing of the switch 63 andenergization of the relay coil 45, whereupon subsequentopening of thevalve 36 and closing of the valvel39 allows air under pressure to beadmitted to the cylinder 6. As air under pressure enters the cylinder 6,the piston plunger 1 and crosshead ID are moved from the right to theleft with respect to Fig. 2, thereby opening the door'l. It should benoted that, when the mercury switch 63 is closed, its cooperatingmercury switch 64 is opened, thus opening the circuit to the switch 55so that, immediately upon moving the switch 63 to a closed position andthe switch 64 to an open position, the electro-magnetic winding 59 isde-energized. With the door I thus moved to its open dotted line ositionof Fig. 1, the user passes outwardly through the door opening 3 andsteps upon the mat 95, thus displacing air within the tube 94 andcausing the mercury in the tubular element 84 to raise thefloat-equipped plunger rod 86 in a direction to close the switch 56. Itshould be noted that, after the user has stepped through th door opening3 and away from the mat 96, the switch 55 will immediately open, due todisplaced air returning to the tube 89. Closing of the switch 56 causesenergization of the electro-"nagnetic winding 66 to simultaneously openthe switch 63 and close the switch 64. Opening of the switch 63 causesthe circuit to be broken to the control 23, whereupon the spring 53 willmanipulate the valves 36 and 39 to permit air to escape from thecylinder 6 to atmosphere, and the spring I5 to move the crosshead l6 toclose the door I. The speed at which the door closes is determined bythe power exerted by the closing spring l5 and the setting of themetering valve 42. Said metering valve-42 may be set to allow air toescape sufficiently slowly so that the person or vehicle passing throughthe door opening 3 has sufficient time to move out of the path of travelof the door I during closing movements thereof. The speed of openingmovements of the door is determined by the differential in pressure ofthe air in the cylinder 6 and tension of th spring [5. This differentialalso is a determining factor, together with the metering valve 42, ofthe speed of closing movements of the door I. As in the case of theresilient tube 89, when the person using the door I has stepped awayfrom the mat 95, air displaced therefrom to the tubular element 84 willreturn, permitting the switch 56 to return to its normal open position.

In the event that a second person steps upon the mat 98, while thepreceding one is treading upon the mat 95 on the outside of the door,weight of the person on the inside mat 96 will cause thecoil 59 to beenergized to cause the dooropening mechanism to continue to functionuntil 11811150 steps upon themat'95 on the "outside of 7 the door. Thus,the door will be held open until all persons in a group have passedtherethrough.

In the modified form of switch shown in Fig. 6, I provide a generallyU-shaped tubular element 96 having an opening 97 in one end thereofadapted to be connected to a conduit 81 and a relatively small opening98 in its other end leading to atmosphere. In the lower central portionof the element 98 is a quantity of mercury X, normally in equilibrium.Between the normal level of the mercury X and the opening 98, a pair ofspaced switch contacts 93 and 100 extend through the side wall to theinterior of the element 9B. The switch of Fig. 6 operates in the samemanner as the structure of Fig. 3 in that, air displaced from aresilient wall chamber will force the mercury X upwardly toward and intoengagement with the switch contacts 99 and I to close a door-opening orclosing circuit thereof. Of course, when the displaced air is allowed toreturn to the resilient walled chamber, the mercury X will return to astate of equilibrium within the tubular element 96, thus open ing thecircuit between the contacts 99 and Hit.

My invention has been thoroughly tested and found to be completelysatisfactory for the accomplishment of the objectives set forth; and,while I have shown and described a commercial embodiment and singlemodification of my improved door-operating mechanism, it should beunderstood that the same is capable of further modification withoutdeparture from the spirit and scope of the invention as defined in theclaims.

What I claim is:

1. Means defining a one-way traffic passage, a normally closed door forsaid passage, a normally inoperative reversible motor for opening andclosing the door, control mechanism for said motor, said mechanismcomprising a first normally pen control circuit to closing of which saidmotor is responsive to open the door, a second normally open controlcircuit to closing of which the motor is responsive to close the door, anormally open control switch in each of said control circuits, operatingmeans for each of said switches, the operating means for the controlswitch of the first circuit being responsive to the presence of traificin a zone adjacent one side of the door to close its switch, theoperating means for the said control switch of the second controlcircuit being responsive to the presence of trafiic in a zone adjacentthe other side of the door to close its switch, two-position switchmeans comprising two pairs of contacts each of which are open in oneposition of the switch and closed in another position of the switch, anelectro-magnetic switch actuator for said two-position switch means,said actuator comprising a pair of windings responsive to energizationof one of which the said actuator moves the two-position switch to oneof its two positions and responsive to energization the other of whichsaid actuator moves said switch to the other of its two positions, eachsaid control circuit further comprising a different one of said windingsand the pair of contacts of said switch means which are closedresponsive to energization of the said winding in circuit therewith.

2. Means defining a one-way trafiic passage, a normally closed door forsaid passage, a normally inoperative reversible motor for opening andclosing the door, control mechanism for said motor, said mechanismcomprising a first normally open control circuit to closing of whichsaid motor is responsive to open the door, a second normally opencontrol circuit to closing of which the motor is responsive to close thedoor, a normally open control switch in each of said control circuits,operating means for each of said switches, the operating means for thecontrol switch of the first circuit being responsive to the presence oftrafiic in a zone adjacent one side of the door to close its switch, theoperating means for the said control switch of the second controlcircuit being responsive to the presence of trafiic in a zone adjacentthe other side of the door to close its switch, two-position switchmeans comprising two pairs of contacts each of which are open in oneposition of the switch and closed in another position of the switch, apair of two-position electro-magnetic switch actuators for thelast-mentioned switch means, each switch actuator comprising amagnetically-responsive armature and solenoid each being operable underenergization to move the said switch means to a different one of its twopositions, each said control circuits further comprising a different oneof said solenoids and the contacts of said switch means which are closedresponsive to energization of the said solenoid in circuit therewith,and means mechanically intercoupling the armatures of the pair of switchactuators to partake of simultaneous movements in opposite directions.

3. Means defining a one-way trafiic passage, a normally closed door forsaid passage, a normally inoperative reversible motor for opening andclosing the door, control mechanism for said motor, said mechanismcomprising a first normally open control circuit to closing of whichsaid motor is responsive to open the door, a second normally opencontrol circuit to closing of which the motor is responsive to close thedoor, a normally open control switch in each of said controlcircuits,fiuid pressure-operated actuator means for each of saidswitches, the actuator means for the control switch of the first circuitincluding a resilientwalled fiuid chamber adapted to be engaged bytrafiic in a zone adjacent one side of the door to close its switch, theactuator means for said control switch of the second control circuitincluding a resilient-walled fluid chamber adapted to e engaged bytrafiic in a zone adjacent the other side of the door to close itsswitch, two-position switch means comprising two pairs of contacts eachof which are open in one position of the switch and closed in anotherposition of the switch, an electro-magnetic switch actuator for saidtwo-position switch means, said actuator comprising a pair of windingsresponsive to energization of one of which the said actuator moves thetwo-position switch to one of its two positions and responsive toenergization the other of which said actuator moves said switch to theother of its two positions, each said control circuit further comprisinga different one of said windings and the pair of contacts of said switchmeans which are closed responsive to energization of the said winding incircuit therewith.

4. Means defining a one-way traflic passage, a normally closed door forsaid passage, a normally inoperative reversible motor for opening andclosing the door, control mechanism for said motor, said mechanismcomprising a first normally open control circuit to closing of whichsaid motor is responsive to open the door, a second normally opencontrol circuit to closing of which the motor is responsive to close thedoor, a normally open control switch in each of said control circuits,fluid pressure-operated actuator means for each of said switches. the

actuator means for the control switch of the first circuit including aresilient-walled fluid chamber adapted to be engaged by traffic in azone adjacent one side of the door to close its switch, the actuatormeans for said control switch of the second control circuit including aresilient-walled fluid chamber adapted to be engaged by traffic in azone adjacent the other side of the door to close its switch,two-position switch means comprising two pairs of contacts each of whichare open in one position of the switch and closed in another position ofthe switch, a pair of two-position electro-magnetic switch actuators forthe last-mentioned switch means, each switch actuator comprising amagnetically-responsive armature and solenoid each being operable underenergization to move the said switch means to a difierent one of its twopositions, each said control circuit further comprising a different oneof said solenoids and the contacts of said switch means which are closedresponsive to energization of the said solenoid in circuit therewith,and means mechanically intercoupling the armatures of the pair of switchactuators to partake of simultaneous movements in opposite directions.

5. Means defining a one-way traffic passage, a normally closed door forsaid passage, a normally inoperative reversible motor for opening andclosing the door, control mechanism for said motor, said mechanismcomprising a first normally open control circuit to closing of whichsaid motor is responsive to open the door, .a second normally opencontrol circuit to closing of which the motor is responsive to close thedoor, a normally open control switch in each of said control circuits,fluid pressure-operated actuator means for each of said switches, saidactuator means comprising a pair of mats disposed on opposite sides ofthe door, a resilientwalled compressible chamber underlying the topportion of each of said mats, a pair of tubular elements associated oneeach with each of said switches, switch-operating members movable in thetubular elements, and fluid pressure conduit means independentlyconnecting each of said chambers with their respective tubular elementswhereby fluid displaced by compression by either of said chambers whenengaged by traffic will move the movable member associated therewith ina direction to operate said switch, twoposition switch means comprisingtwo pairs of contacts each of which are open in one position of theswitch and closed in another position of the switch, an electro-magneticswitch actuator for said two-position switch means, said actuatorcomprising a pair of windings responsive to energization of one of whichthe said actuator moves the two-position switch to one of its twopositions and responsive to energization the other of which saidactuator moves said switch to the other of its two positions, each saidcontrol circuit further comprising a different one of said windings andthe pair of contacts of said switch means which are closed responsive to10 energization of the said winding in circuit therewith.

6. The structure defined in claim 5 in which each of theresiliently-walled chambers of said mats is in the nature of a resilienttube underlying its respective mat and extending about the area thereofin serpentine fashion, one end of said tube being closed and the otherend thereof communicating with its respective conduit means.

7. Means defining a one-way traflic passage, a normally closed doorhingedly mounted in the passage, fiuid-pressure-operated mechanism foropening and closing said door, said mechanism comprising a fluidpressure cylinder, a cooperating piston plunger, a reciprocatory slideelement driven by said piston and cylinder, and linkage connecting saidslide element and said door whereby swinging movements are imparted tosaid door by reciprocatory movements of said slide element,electrically-operated control mechanism for said fluid pressure-operatedmechanism, said control mechanism comprising a first normally opencircuit to closing of which said fluid pressure-operated mechanism isresponsive to open the door, a second normally open control circuit toclosing of which the fluid pressureoperated mechanism is responsive toclose the door, a normally open control switch in each of said controlcircuits, operating means for each of said switches, the operating meansfor the control switch of the first circuit being responsive to thepresence of traffic in a zone adjacent one side of the door to close itsswitch, the operating means for the said control switch of the secondcontrol circuit being responsive to the presence of traflic in a zoneadjacent the other side of the door to close its switch, two-positionswitch means comprising two pairs of contacts each of which are open inone position of the switch and closed in another position of the switch,an electro-magnetic switch actuator for said two-position switch means,said actuator comprising a pair of windings responsive to energizationof one of which the said actuator moves the two-position switch to oneof its two positions and responsive to energization the other of whichsaid actuator moves said switch to the other of its two positions, eachsaid control circuit further comprising a different one of said windingsand the pair of contacts of said switch means which are closedresponsive to energization of the said winding in circuit therewith.

REUBEN E. PETERSON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 955,323 Cutler Apr. 19, 19101,132,849 Howland Mar. 23, 1915 2,011,652 Rowntree Aug. 20, 19352,471,281 Olson May 24, 1949 2,536,489 Burke Jan. 2, 1951

